PCT or CDT during winter

I can't speak for the PCT, but I'd be very concerned about avalanche conditions for a good chunk of the CDT through Colorado, a good portion of the CDT through MT/ID and to a lesser extent through WY.

If you are dead set about hiking in winter and want to be safe(r), consider the Great Mtn Bike Divide Route. It parallels and sometimes crosses/uses the same trail as the CDT. Because it does not go through wilderness areas, it is going to generally be lower.
Mind you, you are still out in winter but the dangers are somewhat mitigated.

http://www.adventurecycling.org/routes/greatdivide.cfm

Mind you I said "safer" and not 100% safe. Not sure of your experience and skill level in winter conditions overnight and backcountry. (Skiing is a rather broad category :) )

Paul,
thanks for your input.

I've had the same thought myself, but have a few questions with respect to the GDMBR; mainly snow cover, and motorized traffic. Got any input there?

To add context; I am well seasoned winter skier (several 100 miles hikes in all types of terrain and weather).

There are no resources on this because no/few people have thought seriously about doing it or done it. With good reason; it'd be an undertaking orders of magnitude harder than the summer versions.

I can answer your questions w/r/t the CDT, to a limited extent.

1: Storms start to fill in the higher reaches in MT, WY, and CO in September. By mid-October it's safe to assume that large stretches of these areas will be difficult to hike through and perhaps require snowshoes and avy awareness. By early January in a generic average year you could probably ski (for example) from Canada to Helena along the CDT route without having to take your skis off, except to cross some windscoured patches and two roads.

2: By early March you should be able to count on skiing almost all of Montana, Colorado, and northern Wyoming. Southern Montana and I assume some places in CO get windblown and can have surprisingly little snowcover, even at 7k or above. I presume the Great Divide Basin would not be skiable, as would large sections of New Mexico.

3: No idea.

4: A serious concern, as a lot of the smaller towns and access road shut down entirely. Indeed many areas would be much more remote. For instance, many/most CDT thrus resupply at a ranch at the end of the Benchmark road in the Bob. This road is not plowed in winter and not all that frequently traveled by snowmachine. The CDT between Marias and Rogers would make a cool ski route, and be almost totally avy safe with a few minor variations.

It would certainly be possible to ski one of the trails, but negotiating a good window of conditions would be thought provoking. On the face of it, assuming something like a five month window for the CDT, you'd be stuck with true winter trailbreaking and avy issues in either Colorado or Montana. A SoBo February start could be pretty rough through to the Winds, but you'd probably have good ski conditions by the time you got to CO (and plenty of dirt in NM). Etc.

A fun question to consider.

Most of the GDMBR in Montana gets lots of snowmachine traffic in the winter, though plenty of it is along roads which get plowed. It would be much less of a wilderness experience, though section like the Swan Valley would probably be doable on skate skis.

To do the entire PCT in winter conditions would be take longer than one winter. Look at it this way; for normal humans, the PCT is a 4-5 month trip when walking on the trail. Now add snow to the equation and it will take longer. Probably a bunch longer, since you have to deal with serious amounts of deep fresh snow, and the accompanying avalanche danger that will require some days of just waiting for the snowpack to consolidate to where it is safe to travel, and some days when it's just too stormy to get anywhere. Now obviously we aren't talking about a winter in the sense of just the official winter, because three months is obviously not possible. But if we say winter starts when the snow begins to accumulate rather than melt after it falls, then maybe you could start in late October if going southbound. If you want to be in snow for all of the mountain parts of the trail (the desert parts you can't do anything about), then you probably want to reach the Mexican border by the start of April so that you still have decent snowpack in the San Gabriels. So you have 6 months. Doesn't really seem doable – and that's before you get into the difficulties of resupply when mountain passes and highways are closed.
But if you do it in sections so that you can go out in the spring when the ski touring is at it's best, then you have only a short time each year to work with. So it's a conundrum.

Now what would be doable, and would be very cool, is to do something like a complete traverse of the Sierra on skis. Say you start in the south somewhere around Kennedy Meadows and go as far north as Lassen. You'd still have to deal with some real winter, because the spring skiing season in the Sierra rarely runs longer than mid-April to mid-May and just isn't long enough for a trip like that, but you could do a lot of it in great conditions. And some of the resupply wouldn't be too bad, between Carson Pass and Lassen the roads mostly stay open.
There's probably similar stretches of the CDT that would be feasible; I'm not familiar with that.

Lots of dirt but …. The San Pedro parks wilderness (the Jemez) in NM tends to get a bunch of snow due to a "rain-shadow" effect and wetter in general, the recommendation being snowshoes until June-ish in normal years according to a couple rangers. Of course what is a normal year anymore, so probably best to call.

Think the CDT is too east in the Gila to require snow mobility devices, unlike the western part which the Grand Enchantment website advised looking into in a strong snow year. West of Socorro, I've seen decent snow in those mountains (not sure if at Pietown or west of the VLA- it's been several years)

Check out Kevin Sawchuck's excellent article on skiing the JMT on this website. It will give you an appreciation for the difficulty of what you are suggesting. The avalanche danger is considerable in the Sierra in the winter.

I'm going to suggest you take some avalanche classes (REI offers them in some stores) as an introduction. I did one that included a day in the Cascades digging pits to check snow-pack conditions and practice sessions with avalanche transceivers. Then seek out some snow-travel courses and seminars that include self-arrest, rope work, and self-rescue sessions on the snow. I took one with RMI on Mount Rainer. Those are skills you not only have to have to undertake such a trip in a safer manner, but I think you should have to grasp just how much of the trip or a leg of it could be delayed many days or more by conditions beyond your control.

Then start using those skills on shorter trips. Of course those can be in winter, but more people gain and practice those skills peak bagging mountains in the best of times. You're more likely to find companions and/or guided trips for such trips than a mid-winter Sierra traverse. Lassen, Shasta, early trips up Whitney are all day- or overnight trips that could let you build experience without the commitment of a Winter Sierra traverse or Winter JMT.

"Check out Kevin Sawchuck's excellent article on skiing the JMT on this website. It will give you an appreciation for the difficulty of what you are suggesting."

+1

"The avalanche danger is considerable in the Sierra in the winter."

Ditto for the Cascades. In either case, if you are contemplating doing this solo, you'd really be rolling the dice due to unpredictable weather and follow on extreme avalanche conditions. Sawchuck's article will give you a very good feel for what even a "section hike" like the JMT entails, even for a superbly conditioned, experienced athlete like him, never mind the entire PCT.